Cisco IOS XE Software ISDN Data Leak Vulnerability

published 2019-09-25 7 y ago modified 2026-06-17 4 mo ago also EUVD-2019-4255

cvss: 4.7; version 3.0, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 1.4%; EPSS 1.4% chance of exploitation in 30 days, percentile 73%
public exploits: 0; none known

A vulnerability in the Dialer interface feature for ISDN connections in Cisco IOS XE Software for Cisco 4000 Series Integrated Services Routers (ISRs) could allow an unauthenticated, adjacent attacker to pass IPv4 traffic through an ISDN channel prior to successful PPP authentication. The vulnerability is due to insufficient validation of the state of the PPP IP Control Protocol (IPCP). An attacker could exploit this vulnerability by making an ISDN call to an affected device and sending traffic through the ISDN channel prior to successful PPP authentication. Alternatively, an unauthenticated, remote attacker could exploit this vulnerability by sending traffic through an affected device that is configured to exit via an ISDN connection for which both the Dialer interface and the Basic Rate Interface (BRI) have been configured, but the Challenge Handshake Authentication Protocol (CHAP) password for PPP does not match the remote end. A successful exploit could allow the attacker to pass IPv4 traffic through an unauthenticated ISDN connection for a few seconds, from initial ISDN call setup until PPP authentication fails.

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: partial
Assessed: 23 mo ago (2024-11-21)

Exploit prediction

1.43% chance of exploitation in the next 30 days, higher than 73% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.0	4.7	CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N
NVD	3.1	7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
NVD	2.0	5.0	AV:N/AC:L/Au:N/C:N/I:P/A:N

Affected products

Cisco Cisco IOS XE Software

Classification

Weakness

CWE-200 Exposure of Sensitive Information to an Unauthorized Actor
CWE-287 Improper Authentication

Technology feeds

Cisco IOS rss critical rss

References

tools.cisco.com /security/center/content/CiscoSecurityAdvisory/cisco-sa-20190925-isdn-data-leak
vendor-advisory

Sources

CVE List CVE-2019-12664
NVD CVE-2019-12664

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Summary